Operating a hydrogen-air fuel cell to generate sufficient electricity to operate a stationary power source or an electric motor vehicle is affected by the amount of hydrogen that can be delivered thereto. The generation of hydrogen by passing steam at or about 700.degree. C. over a bed of iron is well known in the art. Generating hydrogen at elevated temperatures, however, is not practical for most stationary systems or for any automotive systems. Automotively, it is not safe, and it reduces the efficiency needed to compete with heat engines. Therefore, the hydrogen-air fuel cell of this invention must be supplied with hydrogen generated in situ at a practical generating temperature.
The electrical automobile is currently under intense development due to the twin needs to reduce air pollution and conserve fuel resources. One of the major difficulties in the development of the electrical automobile is supplying the power for the electrical drive motors. Such power is currently furnished by batteries. Present battery technology, however, is not capable of providing the energy needed to run the automobile over extended distances.
To the best of the inventor's knowledge, no one has solved the practical problems of using a hydrogen-air fuel cell to generate the electrical energy needed to power an automotive vehicle. There may be many reasons for this, not least of which is the danger of storing great amounts of hydrogen fuel in the vehicle.
This invention reflects the discovery that hydrogen can be generated in situ at reasonable temperature, and then passed into a hydrogen-air fuel cell to generate electricity.
The low-temperature process of this invention is made possible by catalyzing the reaction, by utilizing freshly-ground particles that increase the efficiency of the iron, or both, so that the iron is able to enter into the water/iron reaction at lower-than-normal temperatures.
The iron particles are ground when the vehicle is initially powered and during hydrogen generation. The instantaneous grinding of the iron particles in situ is necessitated because iron becomes rapidly oxidized after grinding. Fifteen minutes after grinding, iron will lose its enhanced reactivity. Therefore, after the initial grinding, the grinding process should continue.
The freshly-ground reactive iron is easily deposited in a compartment in the vehicle. It is easily handled as sealed packet(s) of freshly-ground particulates, but, additionally, it can be freshly-ground in situ aboard the vehicle. The particles range in diameter size from approximately 25 to 1,200 .mu.m; an average-sized distribution is one in which at least 20% of the particles are less than 300 .mu.m in diameter. It is preferable that at least 50% are less than 300 .mu.m in diameter. The average particle density ranges from approximately 1 to 7.8 g/cc, with a non-compressed packed particle density ranging from about 1.5 to 3 g/cc. The particles have a surface area greater than approximately 0.001 meter.sup.2 /g.
A low-temperature iron-water reaction would normally require impractical amounts of iron in order to rapidly generate enough hydrogen at the usual reduced activity. However, using a catalyst greatly enhances the kinetics between H.sub.2 O and iron, thus reducing the amount of iron needed for reaction with the water. For example, when using high- temperature steam for the hydrogen generation, a medium-sized electrically-powered car, which has its electricity generated by a hydrogen-oxygen fuel cell, might consume about 50 pounds of iron during a one-hour trip. In order to obtain the same amount of hydrogen from a steam reaction at 250.degree. C., more than 400 pounds of heated iron would be required under present state-of-the-art methods. Of course, the added weight of the iron would reduce mileage, and the additional 350 pounds of iron would then need the requisite heat to bring it to operating temperature. In other words, the additional 350 pounds of iron would be nothing short of excess baggage. The need to carry and heat more iron than is stoichiometrically required is completely impractical.